Condenser speaker



Emy 3, 1934. p E EDELMAN 1,964,977.A

CONDENSER SPEAKER .Y Filed June 3, 1929 3 Sheets-Sheet l j@ f5 j# 4,

3 Sheets-Sheet 2 July 3, 1934. P, E. EDELMAN CONDENSER SPEAKER FiledJune 3. 1929 my 9, 1994. R E, EBELMAN 1,964,977

CONDENS ER SPEAKER Filed June 3, 1929 5 Sheets-Sheet 3 Fatented July 1i,1934 NETES TATES PATENT GFFCE CONDENSER SPEAKER Chicago, Ill.

Appiication .lune 3, 1929, Serial No. 368,157

4 Claims.

rIlois invention relates to improvements in condenser speakers and themethod of making and using the sa -e. An object of the invention is to'provide an iinproved structure for the speaker apparatus, and foroperating the saine with more perfect reproduction than has heretoforebeen possible in this type of device.

This and other objects are accomplished by this invention, which isfully described in the following specification and shown in theaccompanying Idrawings, in which- F'igure l is a diagram showingsuitable circuit connections for the condenser speaker;

Fig. 2 is a rear elevation of a suitable mounting frame for the acousticcondenser;

Fig. 8 is a front elevation of a portion of the frame of Fig. 2;

Fig. 4 is a sectional view of a part of the condenser assembly showingthe relation of the operating parts;

Fig. 5 is a sectional View of a portion of the dielectric diaphragm andits conductiveI coating;

Fig. 6 is a sectional View of a suitable structure "for the flexibleelectrode diaphragm of the condenser;

Eig. 7 is a section showing part of the condenser diaphragms in amodified structure suit- 'able for use on a collapsible mounting frame;

Fig. 8 is a rear elevation showing a collapsible frame mounting for thecondenser structure of Fig. 7;

Fig. 9 is a diagram showing the use or" a plurality of acousticcondensers according to my in- Ivention;

Fig. 10 is a side View, partly cut away and seetic-ned showing asuitable assembly for a plurality of acoustic condensers connected as inFig. 9; and

Fig. 11 is a diagram showing a circuit for the co-operative use of myacoustic condenser together with an electrodynainic type reproducer.

1n Fig. 1, the acoustic condenser l consists of two operativediaphragms, of which diaphragm 2 'is a porous electrode permeable to airflow and flexible, while diaphragm 3 is impermeable to air iiow,flexible, and carries a conductive coating or electrode 4. Condenser 1is supplied with operating potential from the output transformer 5 of avacuum tube amplifier 11, 12 of customary push-pull design, having aninput circuit 18 which may be connected to a radio set or a talkingniotion picture apparatus. The vacuum tubes 11, 12 are supplied withenergy by a power unit 10 operated through a plug 9 in usual manner. Acondenser 6 in series with speaker 1 is supplied with (Cl. Mii-111)polarizing potential at about 400 lVolts by polarizer power unit 7operated through plug connector 8.

As shown in Fig. 2 and. Fig. 3, the condenser 1 is supported on a woodenframe 14 having a rim 50 lining l5 of rubber material. The soft rubberstrips 15 tend to assist in cushioning the con denser 1 and inmaintaining same taut in use. Wedges 16 permit frame 14 to be expandedto initially stretch frame 14 to make condenser 1 taut, and may be heldin place by glue. Rubber strips 15 may be cemented to frame 14.

As shown in Fig. 4, a minute air gap 17 separates flexible porouselectrode diaphragm 2 from dielectric diaphragm 3. A Contact strip 18 ofsoft lead connects to electrode coating 4 carried on diaphragm 3.Diaphragm 8 is preferably made from empire cloth, varnished with japangoid size and coating with metal foil 4. A soft flexible lead ribbon 19is fastened to contact strip 18 and reinforced by tinsel ribbonconnector 20 to bring a terminal from electrode 4 to lug terminal 23carried on frame 14 by tacks 21. A varnished silk insulator strip 22insulates strips 19 and from tacks 21 which hold dielectric diaphragm 3and flexible electrode 2 to frame 14. A terminal 24 is fastened at 25 toflexible diaphragrn velectrode 2, and fastened to frame 14 by a tack 21.Mucilage containing lamp black or aluminum bronze, or black lead powderis suitable for fastening strips 20, 19, 18 respectively to electrode 4.A small amount of conducting powder in the mucilage is sufficient forthe pur- 13.05,

Another mode of using the conductive mucilage aforesaid is shown in Fig.5. The flexible porous electrode 2 is made from tinsel metal cloth, towhich cross connector soft lead foil strips 27 are glued by conductivemucilage 28 in order to join the tinsel strands of cloth 26 togetherelectrically.

An alternative mode of making the flexible electrode diaphragm 2 isshown in Fig. 6, in which two pieces of tinsel metal cloth 29, arefastened together by conductive mucilage 28, the width of cloth 29 beingcrosswise to the length of the cloth 30 in order to increase thestrength thereof in all directions of tension, and in order further toelectrically connect the individual tinsel strands of said cloths/"29,30. I prefer to have cloth 80 of coarser weave tliana cloth 29, and madewith wider tinsel strands in order to secure greater push on the airwhen diaphragm 2 is flexed in operation.

As shown in Fig. 7, the condenser 1 may be made flexible for portableshipment by the addition of porous fabric cloth pieces 31 and 32stitched thereto at the rim thereof by threads 33. Cross lead foilstrips 18 electrically join the individual tinsel strands of tinselcloth 26, as aforesaid.

As shown in Fig. 8, the flexible roll condenser assembly of Fig.. '7 maybe unrolled and stretched on a collapsible frame 34 having a centersupport 35 and adjusting members 36 to stretch or expand frame 34, sothat end pieces 37 of frame 34 stretch condenser 1, as shown foroperation.

In Fig. 9, a circuit is shown for using a plurality of co-operatingcondenser speakers as aforesaid, whereby different sized condenserspeakers 38, 39, respectively more predominantly responsive to varyingpitch sounds can be selectively connected in correct proportion for mostpleasing reproducing through terminals 44, by means of adjustingresistance 41 having variable terminals 42 and 43 to proportion thevolume of response from each speaker unit 39 and 40 with respect to thelargest acoustic condenser 38 of the assembly. A variable choke coil mayalso be used for member 4l, if desired.

As shown in Fig. l0, the condensers 38, 39 and 40 are mounted in an openframe 49 provided with air holes 52 and porous fabric coverings 51 and50. Frame 52 holds condenser speaker 38 through bracket supports 46.Frame 52 holds condenser 39 through brackets 47. Frame 52 holds acousticcondenser 40 through brackets 48. A distance of at least two inchesseparates the condensers 38, 39, 40 from each other to allow freepassage of sound waves therefrom. This permits the grouping of regulatedvolume of controlled pitch responding condensers in co-operative groupmounting in small space suitable for mounting at the rear of talkingmotion picture screens or in a radio cabinet, as desired.

In Fig. 11, I show how to combine my acoustic condenser reproducer witha dynamic speaker already in use to supplement same with brilliantovertones missed on the dynamic speaker. A vacuum tube amplifier 53 hasan input 54 connected to a phonograph electrical pick-up device or aradio set output. Vacuum tube ampliner 53 feeds a coil 55 which servesas the field coil of dynamic speaker 58, as well as the primary oftransformer 56 which feeds output energy to the dynamic reproducersmoving coil 59 controlled by resistance 57 to proportion the volume withrespect to the volume of response of acoustic condenser 1. Power unit 10and polarizer power unit 7 supply operating energy in customary mannerwhen energized through connector plug 9n attached to a source ofoperating current.

Acoustic condenser 1 receives its audio inputpotential from theterminals of coil 55, that is to say, directly from the plate tofilament circuit of amplifier vacuum tube 53. The co-operative assemblyof Fig. 1-1 affords very pleasing results in that the relative volumesof response in high and low pitch frequencies can be regulated byresistance 57.. v

It may be remarked that both diaphragms 2 and 3 of condenser 1 functionco-operatively and simultaneously with unusually efcient and brilliantresponse to pure tones and accompanying overtones.-

While I- have shown and described but a few embodiments of my invention,it is to be understood that it is capable of many modifications.Changes, therefore, in the construction may' be made which do not departfrom the spirit and scope of the invention as disclosed in the appendedclaims.

I claim:

l. In an acoustic condenser employing a stretched metal fabric, theimprovement which comprises making the fabric in two separate sheets ofthin tinsel cloth one of which is woven i with wider tinsel strands thanthe other, and disposing one of said tinsel cloth sheets crosswise withrespect to the lengthwise tinsel strands of the other sheet, whereby thecombined two cloth sheets are strengthened and electrically connectseparated tinsel strands of each other.

2. An acoustic reproducer combination comprising a vacuum tubeamplifier, a dynamic speaker connected thereto and having a trans`former, a power unit to energize said amplifier and dynamic speaker, anda condenser speaker connected to said vacuum tube amplifier and saiddynamic speaker, characterized by the fact that the transformer of saiddynamic speaker serves as a choke coil for said amplifier output, and asan audio potential feeder to operate said condenser speaker.

3. An acoustic reproducer combination comprising a vacuum tubeamplifier, a dynamic speaker having a transformer, a condenser speakerconnected in parallel with the transformer, and means for polarizing thecondenser speaker.

4. An acoustic reproducer combination comprising a vacuum tubeamplifier, a dynamic speaker having a transformer with primary andsecondary coils, a condenser speaker connected in parallel with theprimary coil of the transformer, and means for polarizing the condenserspeaker, said primary coil serving as a choke coil for said amplifieroutput and as an audio potential feeder to operate said condenserspeaker.

PHILIP E. EDELMAN.

